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Use of Hyphen When Writing Fractions with Words

Date: 01/20/2004 at 10:08:45
From: Colleen
Subject: Writing fractions in word form

Is there one correct way to write a fraction in word form?  I have 
seen one-half and have also seen one half.  I have seen 2/3 written as
two-thirds or as two thirds.  Are both ways (with a hyphen, without a 
hyphen) acceptable, or is only one truly correct?

Date: 01/20/2004 at 13:15:46
From: Doctor Peterson
Subject: Re: Writing fractions in word form

Hi, Colleen.

I usually reserve the hyphen for use in keeping the name of the 
denominator together.  For example,

  1/5 = one fifth

  1/25 = one twenty-fifth

  2/100,000 = two hundred-thousandths

  200/1000 = two hundred thousandths

But you will also see hyphens within numbers when the entire number 
is used in certain special settings:

  One third of a piece

  A one-third share

  A hundred thousand dollars

  A hundred-thousand-dollar income

That may be what you have seen.

See also these pages:

  Writing Numbers with Hyphens 

  Written Form of Decimals 

On the other hand, a web search reveals lots of writing style guides 
that seem to recommend always using the hyphen in fractions, without 
making a distinction as to usage.  Here is just one of many examples: 

    Any two numbers or fractions that are written as words are

      When she reached the age of twenty-one, Sylvia inherited
      three-quarters of a million dollars from her trust fund.

This page doesn't give an example of a fraction, but does clearly 
explain why you use hyphens in the cases I showed above, called
"compound modifier".  An example is

  a woman-hating religion is utterly different from a woman
  hating religion

Here, finally, is a page that ALMOST agrees with me:

  Ask the Grammarian 

    There is some controversy, though, over whether or not to
    hyphenate fractions like three-fourths.  Some sources say to
    hyphenate fractions always and others say to hyphenate them
    only when using them as an adjective, as in a one-half owner.
    I say, keep it simple, stupid: if you always hyphenate
    fractions when writing them out, you have fewer rules to
      "Is a fraction always hyphenated?  No, it is not. A hyphen is
      not used with a fraction that is not serving as an adjective.
      'Today he paid one half of the tax,' not one-half."
      -- The Wordwatcher's guide to Good Writing and Grammar

Here is another site that says not to hyphenate all fractions; but it 
somehow turns the rule on its head just where it is most needed: 

    Hyphenation: Consult the Chicago Manual of Style.

    Fractions and hyphens:  Fractions are almost always hyphenated
    when they are adjectives.

    e.g., "He is one-quarter Irish and three-quarters Nigerian."

    But when the numerator is already hyphenated, the fraction
    itself is not, as in "ninety-nine and forty-four one

    Fractions treated as nouns are not hyphenated.

    e.g., "He ate one quarter of the turkey." 

So both rules are to be found, but the best reason for always using 
hyphens is just to make it easy for people to remember the rule!  I 
still say our rule is best when you want to make sure every case will 
be understood; but then, grammar is not math (obviously!).

If you have any further questions, feel free to write back.

- Doctor Peterson, The Math Forum 
Associated Topics:
Middle School Fractions

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